You wrote "I think I have a heel spur. It started about 2 weeks ago, and it's a sharp pain in my left heel. It comes and goes, but strangely enough, after I walk or run on it a few minutes, it feels better. But sometimes when I first get out of bed, I can barely walk. I've googled it, but wanted to get some opinions on here."
It is more likely, as mentioned, that the fascia on the underside of your foot that connects to the heel bone on the side closer to the toes has gotten inflamed at the insertion point to the heel bone.
At night as you sleep you point your toes, which relaxes the fascia all night, and then when you first step, it has to reach its full length again and minor tears occur on your first steps, which causes pain, until it relaxes a little bit.
If you leave this untreated I have seen on Youtube that you may get a bone spur, as fascia can't stretch much, but your body can grow bone, and the body will grow a bone spur to relieve the pressure on the fascia.
My Suggestion to help would be to never walk barefoot on hard surfaces. So use flip flops at home and in the gym wet areas, and keep them near the bed so you slip into them right away on waking. Never walk barefoot on tile or concrete.
Going to a physiotherapist who is trained in feet is also a good idea as they can see if there is a mechanical imbalance in how you walk. They can put your feet on a kind of 3D scanner and have orthotic inserts made for your main shoes to correct the imbalance. These typically have a spongy hole under the bone spur area, You can start by buying drug store orthotics, but if you have coverage, custom orthotics may be better.
Foot exercises like rolling your foot on a baseball will help, along with loosening the muscles of the calf that connect under around your heel.
Your physio can get you a special sock which pulls your toes up at night and connects to a tight band below your knee just above your big calf muscle. There are also shoes that prevent your feet from pointing, as mentioned above.
If you google plantar fasciitis on Youtube you will find lots of stuff. It takes a while to go away, but you kinda need your feet, so worth the effort.